Abstract 1. 1. Farm raised raccoon dogs weighed significantly more at birth (89.4 g) than blue foxes (72.9 g). Both species gained weight at the same rate retaining the initial difference. 2. 2. For both species, weight specific and age specific cooling rates followed an exponential decay curve. 3. 3. Both weight specific and age specific cooling rates were greater for raccoon dogs than for blue foxes. 4. 4. Solitary newborn pups cooled down about twice as fast as pups in a huddle. 5. 5. Live blue fox and raccoon dog pups weighing less than 65 and 90 g, respectively, cooled down faster than dead pups of the same size. 6. 6. The times within which rectal temperatures of the pups would fall to 30 and 20°C were calculated for typical, practical farm situations.